Recent advances in telephone services have provided telephone customers with a caller identification (ID) feature. This feature allows telephone subscribers to determine the telephone number of a caller if the subscribers have the appropriate caller ID decoding device and subscribe to a caller ID service. Features of these caller ID devices typically include a display, memory for storing the names and telephone numbers of known callers, and memory for storing the telephone numbers of previous callers. The display is used for showing information about the call, including the telephone number of the caller, the caller's name, and the date and time of the call. The telephone company provides the number and/or name of the caller. The date and time may either be provided by the telephone company or the caller ID device.
When a call is made to a person in the U.S. subscribing to a caller ID service, the information concerning the telephone number of the caller is provided on the telephone line via a digital data stream between the first and second ring signals. Other countries may provide the information at different times in the ring cadence. The caller ID device typically decodes the information and displays the telephone number of the caller on a viewing screen of the device. Often the name of the person calling is also displayed if such information is provided by the caller ID service or the device has been programmed to associate the telephone number of the current caller with a particular name. In order for the person being called to determine if the call is one which that person wishes to answer, the video display must be examined. If the video display is in a different location from the person being called, it may be inconvenient or impractical to go to the location where the telephone number and/or name of the caller is displayed.
Prior solutions to this problem have been for the caller ID device to produce an audio signal which identifies the caller or telephone number of the caller. One of these devices is disclosed in U.S. Pat. No. 5,490,205 wherein one of two ringing sounds is broadcast over a loudspeaker to identify specific callers. However, if the person being called is at a telephone extension other than the one connected to the device the broadcast ringing sounds may not be heard. In this case, a single device with an audio signal has little advantage over a caller ID device which merely has a video display. That is, the person being called will still have to go to the location of the caller ID device or to install multiple audio signal devices.
Accordingly, objects of the present invention are to provide a caller ID device which modifies the ring signal on a standard telephone line to produce unique rings on all telephones connected to the same line as the caller ID device, the unique rings being in response to a comparison between the telephone number of the current caller and telephone numbers stored in the device.